As production on the pilot for Joss Whedon’s Marvel S.H.I.E.L.D. TV series gears up to begin in January, two more actors have been added to the cast. Clark Gregg is already set to reprise his role as Agent Coulson in the pilot, and Ming-Na (ER) was recently set as one of the show’s leads, a pilot and weapons expert named Agent Melinda May. Now THR reports that Elizabeth Henstridge (The Thompsons) and Iain De Caestecker (The Fades) have been added to the cast.

Both actors are relative newcomers to U.S. audiences, but Henstridge will play “science whiz” Agent Gemma Simmons, while De Caestecker is set as tech guru Agent Leo Fitz. The two “spend all their time together—mostly bickering—and are masters at a remarkably young age of their respective fields.” Whedon is writing the pilot alongside his brother Jed Whedon and Jed’s wife Maurissa Tancharoen, and he’ll also be directing as well. Should the pilot be picked up to series, the show will likely premiere Fall 2013 on ABC.